In the process of continuously casting metal strips, such as ribbons, it is common practice to dispense molten metal through a nozzle onto a moving chilled substrate. The molten metal solidifies soon after contact with the chilled surface. If the cooling process is rapid enough, a cast product having an amorphous molecular structure is provided. This may be in the form of a relatively thin elongated strip or ribbon which has proven to be effective for winding into highly efficient cores for electrical transformers, and for other uses. Recent developments in the casting of amorphous metal strips are reviewed in U.S. Pat. No. 4,142,571.
It is known in the prior art to cast conventional metal alloys between a pair of opposed counter-rotating belts. In U.S. Pat. No. 3,426,836, for example, molten metal is deposited in a liquid state between a pair of upper and lower moving belts and a pair of lateral belts cooperatively forming a moving mold cavity. The molten metal is chilled in the mold cavity for solidification as it is moved with the cavity. Pressure is applied against the top and bottom belts to urge these belts against opposite sides of the interposed cast metal, the pressure being applied by either pressure rollers or a pressurized fluid, such as compressed air. The applied pressure is designed to compensate for shrinkage of the cast metal upon solidification. A further example of cooling molten metal between a pair of counter-rotating belts is shown and described in U.S. Pat. No. 2,285,740.
In U.S. Pat. No. 4,202,404, an apparatus for producing continuous metal strips on the peripheral surface of a rapidly rotating annular chill roll is disclosed. In this last mentioned patent, once the metal strip is deposited upon the chill roll, an elastomeric flexible belt frictionally engages an arcuate portion of at least 120.degree. about the chill roll with the deposited metal strip positioned between the belt and the chill roll. The belt is wider than the cast strip so that it overlaps the marginal portions of the strip, and direct contact between the casting surface and the flexible belt is established immediately adjacent the portions of the strip. Flexible belts which engage the casting surface in this manner are known in the art as "hugger" belts.
It is also known in the art to use vacuum conveyor belts. The typical vacuum conveyor belt includes a perforated conveyor belt which is moved across a manifold. A vacuum is produced in the manifold and communicated through the perforations in the belt to secure objects on the surface of the belt opposite the manifold. In U.S. Pat. No. 3,642,119, for example, an endless vacuum conveyor belt is supported on its ends by circular pulleys with an elongated vacuum manifold of generally rectangular configuration between the pulleys. A line of perforations is provided in the belts and adapted to register with the slot in the vacuum manifold as the belt moves over the manifold. A similar type of configuration is shown in U.S. Pat. No. 3,889,801. A still further example of a vacuum belt is shown in U.S. Pat. No. 3,419,264.
It has recently been found that amorphous metals can be advantageously cast in a partial vacuum. In U.S. Pat. No. 4,154,283, molten amorphous metal is deposited in a vacuum chamber onto a rotatable chilled cylinder. The pressure in the vacuum chamber is no greater than 5.5 cm. Hg. and quenches the molten metal to form an amorphous metal alloy with reduced surface irregularities and improved tensile strength.